Tire manufacturing industries are known to employ tire building drums comprising two axial portions designed to move axially in relation to each other and each is provided with externally inflatable bladders.
On the said tire building drums, each tire is formed starting from an inner carcass usually comprising an inner elastomeric layer and an outer layer consisting of one or more superimposed body plies.
On the outside of the said body plies, and in given positions along the tire building drum axis, two metal annular beads of any desired configuration and including their respective bead fillers, are placed and clamped into position by the expansion of clamping devices on the drum itself, in such a manner as to secure the said two layers and each bead onto the respective axial portion of the drum. The said two axial portions are then brought closer together so as to deform radially outward the portion of the said two layers extending between the said two beads, and the said bladders are inflated so as to turn over the said beads the parts of the said two layers projecting axially outward of the said beads, in such a manner as to form the said carcass portion.
Whereas, in recent times, feeding and assembly of the aforementioned layers onto the tire building drum have been practically fully automated, serious difficulty has been encountered in automating the handling and assembly of the beads relative to the drum, mainly due to the fact that, when set onto the drum, the beads must be perfectly aligned with the drum axis of rotation.
One known method employed in prior art machines for overcoming this difficulty consists in the use of transfer devices onto which the beads must be fitted manually an in an extremely accurate position. Once fitted with the beads, such transfer and setting devices provide for feeding the beads automatically to the tire building drum and for setting them a given distance apart on the same.
Such a solution presents a number of drawbacks, due to the fact that smooth running of the plant depends on an initial manual operation, i.e. on how accurately the operator fits the beads onto the transfer device. Furthermore, as regards timing of the various assembly stages involved, the said manual operation introduces an independent time variable poorly suited to an automated assembly process.
To overcome the aforementioned drawbacks, machines have been devised on which the beads, positioned not necessarily accurately by the operator, are picked up by a transfer device which transfers them to a setting device designed to center the beads in relation to the tire building drum and to set the beads onto the drum.
Unfortunately, this solution, too, involves a number of drawbacks, mainly due to the said setting device normally comprising two untis located at opposite ends of and connected to the tire building drum.
The presence of the said two units seriously complicates the structure of the drum, unloading of the finished tires and tire size change, thus resulting in a considerable increase in plant cost, and downtime which almost totally eliminates the advantages afforded by automation.